Multi-speed power transmissions used in passenger vehicles have a plurality of forward ratios and a reverse ratio. These transmissions have controls including a range selection mechanism. A majority of these transmissions utilize a manual selector valve which is controlled by the operator through a mechanical linkage or flexible transmitter. The manual selector valve prevents the simultaneous selection of forward and reverse by exhausting the circuit not selected.
The mechanical systems, linkages and/or flexible transmitters, both require routing space between the operator and the transmission. This space is being reduced and the routing of the mechanical system is becoming difficult. To alleviate this design constraint, it has been proposed in some transmission assemblies to use electronic controls. One such example of these devices can be seen in U.S. Pat. No. 5,228,365. This patent describes a system that prevents the simultaneous selection of a forward and reverse condition.
Other devices, such as electric motors, have been incorporated in the transmission control structure to replace the mechanical linkage system. The motor is mounted directly on the transmission case and uses the selector valve to prevent the simultaneous selection of forward and reverse. While the electric motor acts in a manner similar to the mechanical systems, it does not have the same space limitations. However, sufficient space to mount the motor on the transmission case is required.